During supersonic flight, cavities on aircraft affect the airflow across the surface of the aircraft depending on the length to height ratio of the cavity. If the length to height ratio is greater than about 12, the cavity is a shallow cavity and the airflow around the cavity is "closed cavity flow". If it is less than about 12, it is a deep cavity and the airflow is "open cavity flow". Although test results show that a length to height ratio of 12 is the approximate boundary between closed cavity and open cavity flow, this invention is also beneficial for length to height ratios between 9 and 12.
One difference between the two types of cavity flow-fields is the pressure regions formed at the ends of the cavity in supersonic flight. A low pressure region is formed at the front of the cavity and a high pressure region is formed at the rear. In shallow cavities, these pressure areas are separated by a large enough distance that the high pressure region cannot vent to the low pressure region. This results in a large difference in the pressure level between the two regions and leads to increased drag and to difficulty in separating stores (bombs or missiles) from the cavity.
These problems are not characteristic of deep cavities which demonstrate "open cavity flow". In deep cavities, the airflow is essentially undisturbed over the cavity. This is because the high and low pressure areas are not separated by a large distance and the pressure is essentially the same along the floor of the cavity. This means that the cavity causes very little drag and that there is no difficulty in separating stores from the cavity.
Because it is not feasible for all cavities on aircraft to be deep cavities due to space and size limitations, the following are objects of the present invention.
An object of the present invention is to provide a device to cause shallow cavities on aircraft to behave like deep cavities during supersonic flight.
Accordingly, an object of the present invention is to provide a device which will cause the air in the high pressure region at the rear of a shallow cavity to be vented to the low pressure region in the front of the cavity.